This species was first described in 1824 during a French expedition to the Antarctic. Its Latin name 'cruciger' means 'cross-bearing' although it is more commonly called the hourglass dolphin, due to the distinctive markings on its flanks. The hourglass dolphin is the only small dolphin species regularly found south of the Antarctic Convergence. Their calls have never been recorded and a great deal more remains to be learnt about these remarkable cold water dolphins.

Appearance:

The hourglass dolphin is small with a compact body and a striking black and white pattern. In general it has a tall hooked dorsal fin with a broad base and some animals, thought to be adult males, have a marked backward bend approximately half way up the fin. The flippers are long and curved with pointed tips and the flukes are notched with concave trailing edges. The beak is short and stubby and black in colour, extending into a black forehead and back. The dorsal fin, flippers, and flukes are all black as well. There is a white stripe along each side which narrows under the dorsal fin creating an hourglass pattern. There is another black stripe below the hourglass, and the underside of the body is white. The shape of this small oceanic dolphins' dorsal fin is distinctive and along with the unique colouration, misidentification at sea is virtually impossible.

Behaviour:

Hourglass dolphins can generally be seen in groups of 8 animals or less, but schools of up to 60 individuals have been reported. They can swim at speeds up to 22km/h, and are known to be avid bowriders, often approaching boats at great speed and from a distance. They often swim very fast just below the surface creating a large 'rooster-tail' spray (similar to that produced by Dall's porpoise) when they surface to breathe. Hourglass dolphins can be found with many other cetaceans including fin whales and long-finned pilot whales. They are known to feed on small fish including lanternfish, squid, and crustaceans and when feeding often associate with aggregations of seabirds and plankton swarms.

Distribution:

Hourglass dolphins are generally found in a circumpolar band from 45°S to 68°S, although their northern limits are not well defined and they have been recorded as far north as 33°S. Several individuals are known to have been incidentally taken in fisheries however due to their remote habitat, human activities are not thought to pose a serious threat to this species with the probable exception of climate change. Previous surveys estimate there to be approximately 144,300 hourglass dolphins and the IUCN categorises this species as of Least Concern.